Various methods for grinding, polishing, or finishing the surface of a workpiece have heretofore been provided. It is, however, necessary to select a method to be used according to the purpose of finishing or the like or the material or shape of a workpiece. More specifically, for example, casts need to be subjected to rough finishing and then polishing, and on the other hand, some precision components are finally subjected to finishing to have a smooth lustered surface. Further, a grinding method or the like is different between when a workpiece is made of metal and when a workpiece is made of ceramic.
Therefore, it is conventionally necessary to use different abrasive materials or grinding methods for different materials of workpieces or different purposes of finishing or the like, and accordingly it is also necessary to change the grinding tool to be used. For this reason, surface finishing of a workpiece naturally requires time and effort.
It is difficult for any one of the conventional methods to perform finishing or the like of a workpiece having a complicated surface shape efficiently. Particularly, industrial molds or dies or dental implants have complicated uneven surfaces, and therefore polishing of their surfaces requires time and effort. There is also a serious problem with the hygiene of workers because a large amount of dust of abrasive grains is produced in the working environment. As described above, many fundamental problems relating to grinding or polishing, such as poor workability and poor working conditions in a wide range of fields, have not yet been practicably solved.
In light of the above problems of the conventional conditions, Japanese Patent No. 3800610, the entire contents of which are incorporated herein by reference, discloses an abrasive material that enables finishing or the like in a short time even on a complex surface and maintain good working conditions. That abrasive material comprises a plurality of abrasive material particles, each having a core of an artificial composition, such as a synthetic resin foamed material or rubber, and an abrasive grain layer comprising abrasive grains and provided on a surface of the core via a non-curable adhesive as a binder.
Though comprising abrasive material particles having a simple structure in which an abrasive grain layer is provided on the surface of a core, that abrasive material allows a workpiece to have a desired finished surface simply by changing the amount of the abrasive material to be sprayed or the spraying speed of the abrasive material. Further, more precise finishing can be achieved by changing the core or the abrasive grains. The use of a non-curable adhesive as a binder makes it possible, when the abrasive grains are detached from the abrasive material particles due to the use of the abrasive material, to again attach the abrasive grains without again applying the binder due to the long-lasting tackiness of the binder.
Japanese Patent No. 3800610 discloses that the amount of the abrasive material to be sprayed or the spraying speed of the abrasive material is adjusted according to the purpose of surface finishing, and that more precise finishing is achieved by selecting the core or the abrasive grains according to the purpose, but the binder still has a room for improvement from the viewpoint of improving grinding performance because attention is given only to its tack force allowing the abrasive grains to be attached to the selected core or its ability to allow the abrasive grains to be reattached to the selected core.
More specifically, in the abrasive material disclosed in the aforementioned Japanese Patent No. 3800610, the binder has the important function of holding the abrasive grains on the surface of the core. However, that invention does not disclose that when the core or the abrasive grains is/are changed according to the purpose of surface finishing, the type or property of the binder is also changed. That is, the mechanical property or the like of the binder in actual surface finishing is not taken into consideration. More specifically, a grinding force required of the abrasive material is different between when the purpose of surface finishing is rough finishing and when the purpose of surface finishing is polishing, but no measures are taken against the binder to allow the binder to actively contribute to the adjustment of a grinding force.